Specify the Function

Step 3. Specify the function we want to optimize

Now the Function Fitness Generator contains the data we're trying to fit, and we're ready to specify the function that we'll use to fit it.

Selecting and Editing a Functional Form

We could enter our function completely from scratch, but let's see if the Generator has something that comes close to what we need.

Fitness / Common Functional Forms / Double Exponential
looks promising.

A dialog box appears, and the string in its edit field is almost right.

Almost.

We need to change the string from

  A*exp(-k1*$1) + B*exp(-k2*$1)

  A*(exp(-k1*$1) - exp(-k2*$1))

So we click in the edit field and change it,
making sure to get the parentheses right,
and remembering to change the + to a -.

Then we click on the Accept button, which closes the dialog box.
Now our Generator looks like this :

If we need to edit the function later, we can just click on
Fitness / Common Functional Forms / Expression with $1
and a dialog box will appear that has the function string in its edit field.

We have the correct functional form, so we're almost ready to specify the parameters.

But first we should save our work to a session file.

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